“…In contrast to previous beliefs that newborns were free of bacteria, it is now a proven fact that bacteria are present in the endometrium, amniotic fluid, umbilical cord, and meconium (Amenyogbe et al, 2017), and different environmental factors, such as the delivery mode (cesarean or vaginal), feeding style (breastfeeding or formula), gestational age, administration of probiotics or prebiotics, diet, exercise, geography, genetics, and air pollution are the most pivotal determinants for gut microbiota modifications that lead to the development of a mature and healthy gut (Bezirtzoglou and Stavropoulou, 2011;Koren et al, 2013;Tanaka and Nakayama, 2017;Thursby and Juge, 2017;Angelakis and Raoult, 2018;Avelar Rodriguez et al, 2018;Ficara et al, 2018;Leoni et al, 2019). It's quite controversial whether the human placenta includes microbes.…”